The art of corn popping generally involves the use of one of two processes. In one method the popcorn kernels are immersed in or covered with a hot oil which heats the kernel until the starches therewithin expand to explode the outer hull leaving the popped kernel in the familiar blossom-like shape. This process, known as "wet popping" or the heated kettle method, of course, requires the expense of the cooking oil, much of which is wasted. Also it destroys the natural flavor of the popcorn by virtue of providing a coating on the corn.
Of greater importance, however, is the fact that in the wet popping process the corn kernel is heated from the outside in. This generally leaves the heart of the kernel unheated and only the outer portion of the kernel actually expands leaving an uncompletely popped kernel with a hard center core.
The most edible popped corn has a low density for tender chewing and ease of digestion. To achieve this the unpopped kernel must be heated equally through the entire mass to the highest temperature possible before the kernel explodes. This causes expansion to a maximum size creating maximum tenderness. This also causes maximum disintegration of the hull reducing the incidence of hull portions becoming stuck in the teeth or throat of the person eating the popcorn.
The other corn popping process is known as "dry popping" and does result in the greater kernel expansion mentioned above. Here no cooking oil is used but the corn kernels are subjected to dry heat while they are being tumbled or agitated. As the heat contacts different surfaces of the kernel it penetrates into the center. This may be somewhat compared to heat at the center of the earth being built up by intermittent radiation of the sun on different surfaces thereof. As a kernel of corn rolls on a hot surface the cooler side of the kernel draws heat inwardly from the warmer side toward the center of the kernel. In any event, in the dry popping process a greater portion of the corn kernel expands than in the wet popping process, thus rendering the popped corn more edible.
Machines for the dry popping of popcorn have heretofore been generally designed for the commercial market where the corn is popped in large quantities. They have normally been gas heated. Electrical heating means have also been used as exemplified by U.S. Pat. No. 3,931,757 to Goode.
Other machines which utilize the rotary drum concept for corn popping are shown in U.S. Pat. Nos. 2,606,489; No. 3,253,532; No. 2,812,704; No. 1,516,782; No. 1,976,425; and No. 1,937,318. All of these are relatively large expensive machines which are coin operated or used in theaters or the like and do not lend themselves to domestic use.
One of the principal problems in dry popping of popcorn is the separating of the fully popped and edible kernels from those which remain unpopped or only partially popped. These and other problems are believed to be met by the present invention.